net: mscc: ocelot: deal with problematic MAC_ETYPE VCAP IS2 rules

By default, the VCAP IS2 will produce a single match for each frame, on
the most specific classification.

Example: a ping packet (ICMP over IPv4 over Ethernet) sent from an IP
address of 10.0.0.1 and a MAC address of 96:18:82:00:04:01 will match
this rule:

tc filter add dev swp0 ingress protocol ipv4 \
	flower skip_sw src_ip 10.0.0.1 action drop

but not this one:

tc filter add dev swp0 ingress \
	flower skip_sw src_mac 96:18:82:00:04:01 action drop

Currently the driver does not really warn the user in any way about
this, and the behavior is rather strange anyway.

The current patch is a workaround to force matches on MAC_ETYPE keys
(DMAC and SMAC) for all packets irrespective of higher layer protocol.
The setting is made at the port level.

Of course this breaks all other non-src_mac and non-dst_mac matches, so
rule exclusivity checks have been added to the driver, in order to never
have rules of both types on any ingress port.

The bits that discard higher-level protocol information are set only
once a MAC_ETYPE rule is added to a filter block, and only for the ports
that are bound to that filter block. Then all further non-MAC_ETYPE
rules added to that filter block should be denied by the ports bound to
it.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>